In the one-dimensional problem 1D-KRK, all modes \(h_\textbf {k}\)  in Eq. (REF ) are neutrally stable [1]}.
The addition of a higher dimension does not change this behaviour. Through the substitution of the modal form –Eq. (REF )– into the homogeneous version of Eq. (REF ), the following dispersion relation is obtained:
\(\omega = (c_x k_x+c_z k_z) \pm B (k_x^2+k_z^2).\) 
